Circumsporozoite Gene of a Plasmodium Falciparum Strain from Thailand

The nucleotide and deduced amino acid sequences of the CS gene of a Plasmodium falciparum strain from Thailand (T4) are presented. Comparison with the nucleotide sequences of two other P. falciparum CS genes, 7G8 from Brazil and Wellcome from West Africa, shows that: the coding regions outside the repeats of T4 and 7G8 are co-extensive and lack 30 nucleotides present in the Wellcome strain 5' to the repeats; in this region, T4 also differs at 3 nucleotide positions from the 7G8 and the Wellcome strains; in the region 3' to the repeats, T4 differs at two positions from 7G8 and at two other positions from the Wellcome strain--remarkably, all of these differences result in amino acid substitutions; the structure of the tandem repeats in the CS gene of T4 is, 5' to 3', [NANP-NVDP] X 3, [NANP] X 38, which is different from that of the two other strains. Due to the use of synonymous codons, the repetition of the sequence is more precise at the amino acid level than at the nucleotide level. These features contrast with those observed in the CS genes of other plasmodial species.